Model A transmission opinion needed

M

Martinbuilt

Senior Member
Hi.
Yesterday, i opened up my transmission to check and clean everything, before putting it in the car.
I'm new to these cars, and the one i'm working on is built from spares.
For the most part, everything looks pretty good. The only damage, and i think it's significant, is on the center gear in the cluster. I'll add a photo.
I didn't notice any wear, chips or pitting on any of the other gears. Kind of odd, right?
$425 for a new set is not in the budget.
I have 2 other gearboxes that i haven't checked. This one looked like the best candidate.
If i find a better set in one of those, do i use it? I don't know if mixing used gears is acceptable.
Thanks
 

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No money and you have time , give it a try it’ll only cost you time, it doesn’t look to bad, at least pieces aren’t missing ( yet ?)
 
Ideally you should have no pits, chips or any other issues with any of the teeth, so if you can find a better one use it. That being said-if that is the only issue you have with the gears and can't afford a new one, run it. It will be noisy but will hold up. I think mine has pits and I have been running it that way for years-50. I will eventually rebuild my ****** and get a new one.

Mike
 
Thanks for the input.
I'll try to dig through the others this weekend. I have a couple old motorcycles, and parts are sometimes impossible to find. It's good to know i can make due if needed with this machine, too.
 
It'll definitely be a little noisier than normal but the model A. has straight cut gears and it's noisy anyway until you're in high gear!!!
 
I have run cluster gears much worse than yours. I find it common to find fatigue damage / pitting on the 2nd gear of the cluster and the 2nd sliding gear. When driving, I do not spend much time in 2nd gear, so the gear noise doesn't bother me. I would use your cluster gear!
 
Your oil looks kind of milky like there is water in it. Should drain, clean and refill with new 600w or equivalent.
 
The pits are oil reservoirs for the gear :D
I would use it, still better quality than any new made in China ones :eek:
 
Take all the transmissions apart and pick the best parts to build a good working transmission. But pay attention to the design of the parts as there were changes during the production run, mostly in the spacer washers at the ends. The Service Bulletins are a good source of information about the changes. You can buy a new copy from the usual vendors or perhaps find a used one on eBay or from a fellow club member.
 
Hello, I think there was an older post on repro bearings that weren’t too good, if in good condition, original bearings might be a better choice.
 
The older posts on "bearings" pretty much refer to the "needle bearings of the cluster and between the mainshafts. Number A-7118 and A-7121. Some suppliers show these as "B" prefix as the same bearing was used in various transmissions all the way up to the 1940s.

There was a time around the year 2020 when new replacement bearings were sub-standard. MANY threads on that, the primary problem being the way the rollers are landed to their cage (Dimples are the worst.) Hyatt made these bearings originally for Ford - but later switched to be a primarily GM supplier. The Hyatt bearing rollers are seen in two types: solid needles and "helical spring needles. Either of these if they're marked Hyatt I think I would find acceptable.

Another A-71xx family bearing I would consider is Bower - but look to the construction. The needles should have necked down bearing area that mates with the cage. I have a Bower fail that seems to have been "hollow" roller and rolled on rods that made up the cage. This on an "AR" transmission - no evidence of being previously opened. So go figure.

Most suppliers are aware of the bearing issue and have demanded their sources (primarily Chinese) up their game. Buy from an established parts house who will back their reputation.

I recently saw BERLISS 93328 which is an interchange for the A-7121 (1.75") bearing on Ebay. Three for a good price https://www.ebay.com/itm/175359520771. The box says "Made in China."

Berliss 93324 is the interchange for A-7118 (1.5"). One report is Berliss is the brand mostly carried by Model A suppliers now? The suppliers seem a better buy than Ebay on this.

There are MANY interchange bearings listed online from many sources. A lot of the numbers of the interchanges are "near identical" which leads me to believe that brand names share manufacturer source.

As to the transmissions themselves, Bob above I think correct. If you have a problem, it will likely be with 2nd gear, either slider gear or cluster.

My rule of thumb for transmission is either replace all gears with new, or collect used transmissions like pearls on a necklace and mix/match parts from the group to make a "best whole." Never mix new parts with old on gears - shafts and ball bearings probably ok.

At one point I decided to cut an o-ring groove on the cluster gear shaft to stop that leak that normally gets stopped by a seal on the outside of the ******. I had two shafts to perform the groove, and a lathe. One shaft was HARD AS GLASS and I couldn't cut it with carbide tooling. The other shaft cut easily with a high speed bit. The glass hard shaft I "ground" the groove using a tool-post grinder. So check your shafts with a file and use the hard one.

You can forgo the "spacer" in the cluster gear/shaft and use THREE needle bearings for better cluster gear support. I forget if it's two small and one large, or one small and two large.

Joe K
 
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Martin, You are getting two opposite side here. A lot depends on how you intend to use the car. Very light use and you may be able to get by with the transmission as is, but it will likely jump out of gear. If you plan on tours then pick the best parts out of the 3 or buy new gears.
 
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Thanks all. I'll see if i have something better in the other transmissions.
I appreciate all the bearing info in the above post. I've pulled them all, and have decided to reuse what's there. They're perfectly smooth and show no signs of being wet. I don't think there's any harm in trying. I can always pull it if something goes south.
I wish i had tried this sooner. The bikes are a headache.
 
Martinbuilt - I’m also new to Model A’s and rebuilt an extra A trans to get familiar with ‘em.
I agree with nkaminar - take the best case and gears from all three, new bearings, new shafts with o-rings - rebuild the best tower - weld up the forks and shifter ball if needed. Check your clutch cover for worn clutch release shaft and pedal shaft and bushings.
Good luck!��☘️
 
That gear with the wear is the part of the cluster that meshes with first gear, usually in my experience it is caused by the engine either not idled down enough by either idle screw too high or not retarding the spark at idle, or it's caused by not letting the cluster spin down when getting ready to engage first. I set my idle when warm at full retard to let me get into first after counting to 3 seconds. As too what is to be done, I agree with the line of thought that it is best to get the best gears you can. In my opinion, try not to mix and match new and old gears since the old gears are mated together, mixing new and old can lead to noise and wear. if it isn't too bad, just put new bearings and gaskets in the ****** and leave it be. If they are badly chewed up, get all new gears and shafts along with the aforementioned parts. Best also to get all the gears from the same place as they likely will all be from the same manufacturer. Button the ****** up and get-er-done!
 
Clean everything. Dress all flat surfaces with a flat file, replace all the bearings including the pilot and throw out bearing. Check for wear of the clutch fork and shaft, maybe new pedal bushings?
Rebuild the shift tower including the forks. Make sure the u joint is in good shape.
Do all this and the transmission will shift nice and should last for years.
 
Use a modern gear GL5 gear oil that has a high anti-squeeze-out and synthetic content. I consider the 600W stuff to be high priced snake oil! I run 75W140 or 85W140 which ever is the least expensive at Walmart.
 
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Thanks again.
I went through everything i have this morning. All the best parts are in that first box. I'll clean everything up, get some bearing and gaskets, and see what happens. Pedal shaft bushings are on the list.
It's got a heavy retainer plate on the shafts. The Brattons catalog identifies it as an early trans? '28-ish?
 
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